I recently purchased several Noble Company products. I've phoned their technical support people several times to ask questions. They are very helpful and knowledgeable. I suggest you call them for any questions you have.

These things are like maybe 3" deep, and at 1/4" per foot, that's 1/16" of an inch. It would be hard to tell! Either case, it's not hard to get some slope when you set the tile on that bottom edge. I don't remember if those have a coating on them, or it's all foam. IF it's all foam, it would be easy to sand a slight slope prior to installation, or even after it was installed if you wanted to.